PFAS Experts Symposium 2: Evolution from past to present, current efforts, and potential futures

Due to the diverse chemistries of per- and polyfluoroalkyl substances (PFAS) and their apparent recalcitrance to natural biological and abiotic transformation processes, remediation of this class of compounds in groundwater environments is much more challenging than that of other common contaminants such as chlorinated solvents, hydrocarbons, methyl tert-butyl ether, and 1,4-dioxane. Overall, the groundwater remediation community is faced with substantial challenges that will require both continued enhancement of existing technologies and development of new technologies and strategies to manage PFAS-impacted sites. Fortunately, an extraordinary breadth and depth of ongoing research in PFAS remediation is funded through a variety of different agencies and organizations. This research can be organized into three main categories: (1) nondestructive approaches that remove PFAS from water and other matrices; (2) destructive technologies that break carbon-fluorine and carbon-carbon bonds to create nontoxic products; and (3) coupled systems that concentrate and then destroy PFAS. As with previous groundwater contaminants, an initial focus on ex situ PFAS treatment is now slowly evolving to include more in situ research. However, as of 2021, there are no practical groundwater remediation technologies that have been shown to destroy target PFAS (i.e., mineralize and/or create nontoxic products) in situ at full-scale field application. While the historical goal of in situ treatment for most contaminants has been destruction, practitioners, facility owners, and regulators may need to alter their expectations and objectives for PFAS, at least in the short term, to management strategies that include treatment at receptor locations to avoid exposures and adsorption-based attenuation strategies for some plumes. These approaches can be used as practical alternatives to PFAS destruction or to buy time until promising technologies become both commercially available and accepted by the industry. The success of any remedial effort typically depends upon meeting regulatory criteria, which in the case of PFAS, are currently in flux at the federal level and differ by orders of magnitude among state regulatory bodies. While this is understandable given the uncertainty and complexity of this issue, setting firm, consistent, and attainable regulatory standards is necessary to provide researchers and practitioners with necessary benchmarks for remediation technology development and commercialization.